The endothelium plays an important role in the regulation of localized immune responses and trafficking of leukocytes in normal and diseased tissue. Microvascular endothelial cells, through the selective expression of cell adhesion molecules and cytokines, perform the crucial function as "gatekeepers" of inflammation by controlling the physiological homing of leukocytes to specific immune compartments and modulating the abnormal recruitment of immune cells into inflamed tissues. The acquisition of fundamental knowledge regarding the role of vascular endothelium in mucosal immunity and inflammatory bowel disease (IBD) has been hindered by the lack of availability of these cells in vitro. To overcome this obstacle, we have developed a novel methodology to isolate, culture and study microvascular endothelial cells from normal and IBD-involved mucosa. These novel approach will be used to test the following central hypothesis: local activation of intestinal mucosal micro vascular endothelial cells plays a pivotal role in the inflammatory response of IBD. This hypothesis will be tested by three specific aims: 1) Define the phenotypic and functional characteristics of microvascular endothelial cells from normal and inflamed human intestinal mucosa. This will include their isolation, and phenotypic and functional characterization; 2) Investigate the mechanisms of mucosal endothelial cell activation by inflammatory mediators. This will include the evaluation of phenotypic, functional and molecular changes induced by cytokines, bacterial products and leukocyte interaction; 3) Explore the effect of oxidized lipids and lipoproteins on mucosal endothelial cell activation. This will determine which and how specific oxidized lipoproteins modulate the phenotypic and functional characteristics outlined in the previous aims. To achieve these goals, the Mentored Clinical Scientist Development Award will provide broad and essential training in laboratories dedicated to endothelial cell biology, mucosal immunity, regulation of activation genes, and biology of lipoproteins. This extended and formal training experience will lead to the acquisition of new expertise in unique areas outside of traditional IBD research, bringing a fresh new perspective to the understanding of the mechanisms of gut inflammation. Information generated by this project will help characterize a still unexplored population of mucosal cells, define fundamental alterations in endothelial- leukocyte interaction in IBD, and explore possible mechanisms linking dietary lipids to the initiation and maintenance of chronic mucosal inflammation.